We remember the big snows, the floods and the dry spells. Do weather trends emerge from tracking the highs, lows and lengths of the seasons?

Dick Kalnicky

Everybody talks about the weather, but a few of us try to figure it out. In Wisconsin, dozens of cooperative observers and several U.S. Weather Bureau offices have regularly observed the weather across the state and accurately recorded conditions since 1891. What do these continuous records show? How do we distinguish normal from extreme weather, and can this knowledge help us see future trends?

Tracking weather patterns teaches us about human nature as well. Most people don't recall the weather last week, let alone last year. We don't remember weather averages, but we revel in memories of the extreme weather that affected our lives. For instance, many people in southern Wisconsin remember a series of soggy days last June followed by a rainfall of more than seven inches that turned back yards into lakes and basements into swimming pools. Last winter in late January and early February, temperatures dipped to record lows and many schools closed for several days because it was too cold to start the buses and too dangerous to walk outside without plenty of wraps and skin protection.

I remember being a sophomore at Boyceville High School back in January 1963 when school closed for three days because it dipped below -30 F. Imagine what it was like in January 1912, the coldest month in 105 years when the average Wisconsin temperature was -2.5 F!

I also remember the fall of 1969, beginning graduate school at Madison, a full 220 miles southeast of home and that much closer to Florida. My dreams of milder winters were quickly put to rest by the brutal Januaries of 1970-72 which were a full seven degrees colder than the three previous winters.

Two recent summers in Wisconsin took us from the freezer to the fryer. In 1992, following the eruption of Mount Pinatubo in the Philippines, huge amounts of volcanic ash were suspended in a band that spread worldwide. That summer, it was too cold in my Madison garden for sweet corn to produce cobs – an average temperature of only 65.5 F; a full four degrees below the norm. Only the summer of 1915 was colder since records have been kept. On the other hand, the summer of 1995 was the warmest on record in Madison with an average temperature of 74.6 F.

Drought and flood years are equally memorable. You may remember back to 1988 when the state was so dry that the Mississippi River had too little flow to sustain boat traffic. If you lived through them, the Dust Bowl years coupled with the Great Depression caused major migrations from the Great Plains states.

The weather can be downright devastating when several unusual seasons follow back to back. The great floods of the summer of 1993 took their toll following almost 16 inches of rain. The stage for disaster had been set by high rainfall in 1991 and a cold summer in 1992, which lowered evaporation and raised groundwater levels. This was followed by a wet spring in 1993 when 10.41 inches of rain fell in the Midwest. The ground was simply saturated. The additional 16 inches of rain that summer could not soak into soil fast enough. It cascaded down slopes and waterways, flooding out low lands and river valleys. We actually had more rain in the summer of 1980 (16.24 inches), but those storms followed a dry spring. Consequently, few areas flooded.

Tracking the temperature

After tracking the weather year to year for 105 years, hindsight provides some trends. Wisconsin's mean temperatures can be divided into four periods: the 1890s through 1920s when temperatures fluctuated both above and below the mean temperature; the 1930s, '40s and early '50s when temperatures were consistently above normal; the late 1950s through the early '80s when temperatures were consistently below normal; and the late '80s through the present when temperatures appear to fluctuate above and below the norm again.

Temperature trends for the winter and summer seasons were nearly identical to the annual averages, but the winters were more variable. Winters during the late '70s were consistently eight degrees colder on average than winters in the 1930s. So, among other things, when your grandparents and parents carp about how much tougher life was during the Depression, remind them that they are only talking about economic conditions. If you are in your thirties and forties, you experienced tougher weather as a child than your elders!

In summer, the differences between the highest and lowest means were about three degrees. That may seem small, but if such subtle changes are sustained, the landscape ecology would shift dramatically. A mean summer temperature change of only two degrees could change the look of the Northwoods, shifting the dividing line between Wisconsin's southern oak savanna and our boreal northern forest about 80-100 miles northward. Eventually the predominant stands of conifers so noticeable north of a line from St. Croix Falls to Wausau to Oconto Falls would not be common until one traveled as far north as the state border between Wisconsin and the Upper Peninsula of Michigan.

Precipitation trends

Except for a short period in the late 1980s, rain and snowfall amounts have been on the high side since 1970, mostly due to really wet summers. The droughts in the Dust Bowl days of the '30s followed several years of back-to-back dry springs and summers. Groundwater levels took a long time to recover from this extended dry period.

I saw a less dramatic example for myself on the family farm. In the late 1950s, we regularly harvested crops of hay from lowlands that would be classified as seasonal wetlands. By the 1980s, after several seasons of cool temperatures and above-average rainfall, these fields had mostly become marshland. Groundwater in this area has risen at least four feet. In fact, my parents had to install a sump pump in the farmhouse in the late 1970s in a basement that was within and above bone-dry soil when the house was built in 1959.

Greenhouse or not?

Worldwide, mean temperatures reached their highest levels in the past 100 years during the 1980s and 1990s. Many scientists attribute part or all of these temperature increases to the greenhouse effect – where sunlight reaching the Earth is radiated from the surface and trapped by ozone, water vapor and carbon dioxide in the atmosphere. Although Wisconsin's temperatures in the last 10 years were warmer than they were from 1956-85, they are still well below the average temperatures of the 1930s and 1940s.

However, the fact that average temperatures here have not reached an all-time high does not discount a greenhouse effect. Climatic changes are not constant across the globe; there is substantial regional variety. For example, worldwide temperatures from 1961-70 were somewhat cooler than they were from 1931-60. However in the United States, parts of the West were warmer than the norm from 1961-70, while eastern states (including Wisconsin) were quite a bit cooler. Even climatic models of the greenhouse effect show regional variety as part of the overall trend of global warming.

Some experts believe the greenhouse effect spawns stronger storms because the warmer temperatures provide more moisture and energy to fuel violent weather. Could this explain why Wisconsin's average precipitation has been higher since 1970?

Hard to tell.

The changes that we notice year to year are so subtle that only the hindsight of a few decades allows definite patterns to emerge. For instance, average rainfall increases of only two inches over a 25-year period would increase groundwater levels by four feet. A four degree temperature change during our coldest six months can increase our heating bills by more than 10 percent. During the past ice ages, world mean temperatures were only 10 degrees colder than they are now.

Wisconsin's climate has changed many times throughout our recent and not-so-recent history. These subtle swings bring big environmental changes that define our floodplains, groundwater levels, native vegetation, food supplies and energy use. In following the past 105 years of weather records, it's clear why the art of long-range weather prediction is so open to interpretation. The daily, seasonal and even yearly swings mask the small changes in mean temperature that could tell us if the next swing will head toward the greenhouse or the ice box. It takes a lot of hindsight to sharpen the forecasts.

Live with it!

Whether the weather be fair or whether the weather be not,
Whether the weather be cold or whether the weather be hot,
We'll weather the weather, whatever the weather,
Whether we like it or not!

–Words and music published by the Presbyterian Book Store, New York, New York)

So how tough are we?

+50 F/ 10 C Wisconsinites plant gardens

+40 F/ 4 C Californians shiver uncontrollably; Wisconsinites sunbathe

+35 F/ 2 C Italian cars don't start

+32 F/0 C Distilled water freezes

+30 F/-1 C You can see your breath
You plan a vacation to Florida
Wisconsinites eat ice cream

-60 F/-51 C Walruses abandon the Aleutian Islands
Sign on Mount St. Helens: "Closed for the Season"
Wisconsinites put away their gloves and take out the mittens
Boy Scouts in Eau Claire start the Klondike Derby